364 DEEP SEA FISHES. 



3facrurus camts and Ilahsaunis radiahis, Plate LXXXIV., exemplify very 

 diverse forms, dwelling at the bottom, secured from moderate depths. 

 Compared with 31. ungnlkcps, M. camts, from 210 fathoms, has a larger eye 

 and a somewhat smaller degree of development in the disks of the oral series, 

 and the frontal disks are quite as well developed as any of the others. 

 This species is an intermediate between Macrurus and Trachyrhynchus; 

 there are 68 cephalic disks. On Halosaurus the relative positions of the 

 disks (which are no doubt lanterns and flash lights) and the eyes are much 

 like that of a dark lantern and an observer who keeps himself out of sight 

 in the shadow while throwing the light upon objects around him. On some 

 species the disks are covered by screens which prevent escape of the light 

 in other directions than downward away from the body. On the npper sur- 

 faces of the head the disks are comparatively few, are much less developed, 

 and are not apparent in the cranials backward of the orbital branches. 

 Backward of this point the cranials and the aural branches, which latter 

 unite on the occiput, are hard-walled tubes and much more primitive in char- 

 acter; but on the body the greatly differentiated disks reappear, closely 

 imderlaid by the especially large branch of the vagus by which they are 

 innervated. In the figures this nerve would appear to be forward of the 

 pectorals ; in reality it passes above and down inniiediately behind them. 



